For example, let's say a female friend asks you "what did you do last night?" and you respond with "Oh, I went for dinner with Alex and Michael, then we went to catch a movie" but you omit that after that, you went for drinks with Chrissy. Is this considered lying to you?

(This situation did not happen, it's just an argument i'm having with someone).

I consider it a form of lying. While technically, what you said is true, you're purposely not mentioning a part of the story that has some weight on it and you're misleading them.

If you think it's not on the up-and-up, it's probably lying by your definition. It just might not be by someone else's, since we're all different. Can't expect people to adhere to your values, even if they make perfect sense to you. Some people need to lie in order to function.

Well, for starters, who is this female friend? What is the problem if he went out with Chrissy if this female friend is not his girlfriend? Ok, so if he was interested in the friend and Chrissy, but hasn’t gotten anywhere at this point with either of the girls, sure, I’d say don’t tell her about it. There’s nothing wrong with “planting the seeds” and other people shouldn’t need or care to know about it.

For example, let's say a female friend asks you "what did you do last night?" and you respond with "Oh, I went for dinner with Alex and Michael, then we went to catch a movie" but you omit that after that, you went for drinks with Chrissy. Is this considered lying to you?
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This shouldn't be a question. If going for drinks with Chrissy is what you did last night, then that's what you answer the question with, unless you're interested in lying.